Abstract:

Rutile is much less active than anatase and brookite for the photocatalytic degradation of organic pollutants in aqueous solution. In this work, we found that addition of a trace amount of CuWO₄ greatly accelerated phenol degradation in an aerated aqueous suspension of rutile. The increased rate was not only much higher than those of anatase and brookite, prepared at the same temperature (600 ℃), but also increased continuously with the sintering temperature of rutile from 150 to 800 ℃. These observations indicate that the high intrinsic photocatalytic activity of rutile produced at a high sintering temperature can be exploited by using co-catalyst CuWO₄. Furthermore, as the amount of CuWO₄ added to the suspension increased, the amount of H₂O₂ produced in the presence of excess phenol increased and then decreased; the trend was similar to that observed for phenol degradation. The observed positive effect of CuWO₄ is mainly caused by solid CuWO₄ rather than Cu²⁺ ions in aqueous solution. A (photo)electrochemical measurement showed that interfacial electron transfer occurred from the irradiated rutile to CuWO₄. This would improve the charge-separation efficiency, and consequently increase the rates of O₂ reduction and phenol degradation.

Key words: Rutile, CuWO₄, H₂O₂, Organic degradation, Photocatalysis, Charge transfer